According to Jain Dharma, this cannot be given as a simple “X years ago” in our normal calendar.

Bhagwān Rishabhdev (Ādināth) is the first Tirthankar of the current avasarpinī (descending half-cycle of time). His janma and Tirthankar‑hood are placed in the very early part of this cosmic era, counted in crores and crores of years, far beyond recorded human history.

Jain scriptures describe his time using cosmic units (ara, kalpa, sāgaropam, etc.), not in ordinary years like “10,000 years ago.” So from the traditional Jain viewpoint:

• We cannot convert “when he became Tirthankar” into an exact number of years ago in the modern sense.
• What we can say clearly is: it was countless millions of years ago, at the beginning of this current avasarpinī, not in recent historical time.

You can read more here about Rishabhdev Bhagwān’s time and life story